Method ringing (also known as scientific ringing) is a form of change ringing (the practice of ringing a series of mathematical permutations on tuned bells, rather than a melody). In method ringing, the ringers are guided from permutation to permutation by following a specific algorithm, called a method. Where the treble bell follows exactly the same pattern as the other bells it is called a principle. The underlying mathematical basis is intimately linked to group theory.